#include <iostream>
#include <assert.h>
#include <unistd.h>
#include <cstdio>
#include <cstring>
#include <string>
#include <sys/types.h>
#include <sys/wait.h>
using namespace std;

int main()
{
    //1.创建管道
    int pipefd[2] = {0};//pipefd[0]:读端， pipefd[1]:写端
    int n  = pipe(pipefd);
    assert(n != -1);//release版本assert无效
    (void)n;//证明被使用过

#ifdef DEBUG
    cout << "pipefd[0]:" << pipefd[0] << endl;
    cout << "pipefd[1]:" << pipefd[1] << endl;
#endif

    //2.创建子进程
    pid_t id = fork();
    assert(id != -1);
    if (id == 0)
    {
        //子进程
        //3.构建单向通信的信道,父进程写入，子进程读取
        //3.1关闭子进程不需要的fd
        close(pipefd[1]);
        // close(pipefd[0]);
        char buffer[1024];
        while (true)
        {
            ssize_t s = read(pipefd[0], buffer, sizeof(buffer) - 1);
            if (s > 0)
            {
                buffer[s] = 0;//添加 '/0'
                cout << "child get a message[" << getpid() << "] father# " << buffer << endl;
            }
        }
        //close[pipefd[0]];
        exit(0);
    }
    //父进程 - 写
    //3.构建单向通信的信道
    //3.2关闭父进程不需要的fd
    close(pipefd[0]);
    string message = "我是父进程，我正在给你发消息";
    int count = 0;
    char send_buffer[1024*8];
    while (true)
    {
        //3.2 构建一个变化的字符
        snprintf(send_buffer, sizeof(send_buffer), "%s[%d] : %d",
                message.c_str(), getpid(), count++);
        //3.3 写入
        write(pipefd[1], send_buffer, strlen(send_buffer));
        //3.4 故意sleep
        sleep(1);

    }
    pid_t ret = waitpid(id, nullptr, 0);
    assert(ret < 0);
    (void)ret;


    close(pipefd[1]);
    return 0;
}
